1. The Field of the Invention
The field of the invention is optical cables for riser applications.
2. Background of the Invention
The National Electrical Code (NEC) requires that cables to be located within buildings meet higher requirements for smoke and flame resistance than cables to be located outdoors. Among several different possible cable constructions is the "loose tube" construction, in which each buffer tube contains at least one optical fiber and a gel. Since the presence of gel makes it more difficult for a cable to meet the NEC smoke and flame requirements, riser rated cables generally lack such gels. An exception is the cable design as shown in the commonly assigned U.S. Pat. No. 4,892,382, incorporated herein by reference.
Therefore, it is believed that the cable according to the present invention, which utilizes a design markedly different from that disclosed in U.S. Pat. No. 4,892,382, would constitute an advance over the prior art.